Fluorine-containing polymers are used in various fields such as automobile, semiconductor and chemical industries, by virtue of unique properties of the polymer such as weather resistance, heat resistance, chemical resistance, low refractive property, low dielectric property, water- and oil-repellency and lubricity. Those properties are derived from fluorine atom, and are generally expected to be improved as fluorine contents in the polymer increase. However, aliphatic fluorine-containing polymers are adversely affected by the increase of the fluorine contents. For example, the solubility of those polymers in general organic solvents decreases, resulting in difficulty in handling. In addition, the intermolecular force thereof decreases, resulting in deterioration in its adhesion to other base materials. Accordingly, there has been a demand for developing a method of producing more versatile fluorine polymers by adjusting the fluorine contents and a structure of principal chain freely to thereby obtain desired properties.
On the other hand, there have been proposed a variety of fluorine-containing polymers to which crosslinkable groups were introduced, in order to improve durability and/or hardness (see, for example, JP-A-2003-26732 (“JP-A” means unexamined published Japanese patent application), JP-A-2006-299218 and JP-A-2006-316113). It is impossible, however, to adjust the structure of principal chain and fluorine content of those polymers freely, because they are each obtained by introducing a crosslinkable group to a polymer prepared according to a conventional method (radical polymerization), and there is a limit in available monomers.